U.S. Pat. No. 5,067,322 issued to David G. Beers on Nov. 26, 1991, for "Refrigerator With Spine Fin Evaporator", and assigned to the same assignee as the assignee of this application, discloses a spine fin evaporator for a refrigerator. The spine fins of the evaporator of the aforesaid Beers patent, which is incorporated by reference herein, provide a large heat exchange area per unit length of the evaporator conduit or tube. This increase in the heat exchange area per unit length of the evaporator conduit or tube enables the size of the evaporator to be reduced to increase the usable storage space of the refrigerator.
The air being refrigerated by the evaporator is laden with moisture, and the evaporator normally operates at frost collecting temperatures. The moisture laden air flows around the fins and frost tends to build up quickly at the inlet end of the spine fin evaporator. This build up of frost requires the evaporator to be defrosted fairly often so that the overall operating efficiency of the refrigerator is reduced.
The spine fin evaporator of the present invention satisfactorily solves the frost build up problem through forming the evaporator in first and second sections of contrasting shapes when viewed from the end of the evaporator. Each of the first and second sections is formed of elongated straight runs, which have fins thereon and have their ends connected by return bent ends. The elongated straight runs of the first section, which has air flow over it initially, are arranged in two rows spaced sufficiently from each other to allow frost build up without air blockage and to enhance the ease of defrosting; the fins of the first section do not overlap.
The second section has a plurality of rows of the elongated straight runs with their fins overlapping. The overlapping of the fins provides a highly efficient heat exchange relation between the refrigerant in the evaporator and the air flowing thereover.
The close packing of the elongated straight runs of the second section of the evaporator provides a relatively large surface area of the evaporator for each cubic foot of space. This permits more usable space in the refrigerator.
The close spacing of the second section, with its overlapping fins, makes this section relatively intolerant of frost build-up; that is, frost build-up on the section will more quickly close the various passage between the fins and will cause the air to flow around the outside of the evaporator. Also, effective defrosting of the second section is more difficult as the close spacing of the fins means the frost must essentially comletely melt in order to fall off.
The two sections work in concert to provide a highly effective evaporator.
The first section collects relatively large amounts of frost build up which, because of the size of the spacing between the two rows of the evaporator, it can easily accommodate. Since the first section removes most of the moisture from the air, the first section aids in preventing any significant amount of frost from gathering on the closely packed second section so as to reduce the amount of frost to be removed therefrom.